When it was introduced about five years ago, GM's mild hybrid technology was initially written off as an underperforming slightly electrified drivetrain, meaning it reduced performance and didn't really help that much in the fuel economy department, the two things GM had originally touted as beneficial features. But after some tweaks and a name change to eAssist, the technology has improved, and in late 2011 it became the base 2.4-liter engine on the 2012 Buick LaCrosse.

For 2013 Buick, has extended it to the Regal, which now has the formerly optional 2.4-liter eAssist as the base engine. The 2013 Chevrolet Malibu Eco will be the third GM nameplates with eAssist when it's added to the mix.

Essentially a way to turbocharge a gas engine with electrons, the eAssist system couples a 2.4-liter engine to an oversize starter motor/generator and a large battery pack in the trunk. The powerful starter motor adds a way to boost the engine's power with electricity when accelerating, recapture energy when braking and turn off the engine when coming to a step, then instantaneously start it back up. Altogether the system can add 15 to 20 percent in fuel economy without diminishing performance.

For the 2013 Regal, this translates to an EPA-rated 25 mpg city and 36 mpg highway. That's a significant improvement over last year's 19 mpg city and 31 mpg highway with the base engine. The sacrifice comes in reduced trunk space to accommodate the larger battery pack stored there. Buick hasn't yet released pricing on the 2013 Regal, but the eAssist tech was a $2,000 option on last year's model, which had a base price of $27,940.

Given the expansion of eAssist to multiple vehicles in the last year, GM will continue to make the technology available to many of its other nameplates in the near future, with the Impala (based on the LaCrosse platform) likely to see the technology next.

What it means to you: GM's eAssist is a fuel-saving technology that's starting to make its way across many of the company's brands, now that it's standard on the Buick LaCrosse and Regal and optional on the Chevy Malibu.

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